Dialkoxyxanthogendisulphides

ABSTRACT

Dialkoxyxanthogendisulphides, their production by reacting an alcohol and carbondisulphide in the presence of alkali and subsequent oxydation, use of these dialkoxyxanthogendisulphides as molecular weight regulators in polymerisation processes and a mixture of chloroprene-copolymers made in the presence of dialkoxyxanthogendisulphides.

United States Patent [191 Mayer-Mader et al.

[ Apr. 1, 1975 I DIALKOXYXAN'IHOGENDISULPHIDES [75] Inventors: Rudolf Mayer-Mader, KoelmJurgen Boldt, Opladen, both of Germany [73] Assignee: Bayer Aktiengesellschaft,

Leverkusen, Germany [22] Filed: Nov. 9, 1972 [2|] Appl. No.: 305,133

UNITED STATES PATENTS 1.491.021 4/1924 Adams 260/455 B 2375,08} 5/1945 Cooper I. 260/455 B FOREIGN PATENTS OR APPLICATIONS 1.161833 2/1964 Germany 260/455 B 733.532 5/I966 Canada 260/455 B Primary E.\'aminerLewis Gotts Assistant Examiner-D. R. Phillips Attorney, Agent, or Firm-Connolly and Hutz [57] ABSTRACT Dialkoxyxanthogendisulphides, their production by reacting an alcohol and carbondisulphide in the presence of alkali and subsequent oxydation, use of these dialkoxyxanthogendisulphides as molecular weight regulators in polymerisation processes and a mixture of chloroprene-copolymers made in the presence of dialkoxyxanthogendisulphides.

5 Claims, No Drawings 1 DIALKOXYXANTHOGENDISULPHIDES This invention relates to dialkoxyxanthogendisulphides. to a process for their production andto a process for polymerising dienes in the presence of these dialkoxyxanthogendisulphides.

The dialkoxyxanthogendisulfides according to the invention correspond to the general formula (I):

R-O-C-S-S-C-O-R (I) wherein the R's are equal or different and each represents wherein R is alkyl having I to l() carbon atoms;

R is linear or branched alkylene having 3 to 10 carbon atoms.

R is alkyl having 3 to l carbon atoms;

n and n are 2. 3 or 4: and

m are l or 2.

Preferably both Rs are equal. The following dialkoxyxanthogendisulfides are preferred:

di( 3,(i-dioxaheptyl-l )-xanthogendisulphide,

di( 3 6-dioxaoetyl-l J-xanthogendisulphide.

di( 3,6-dioxanonyl-l )xanthogendisulphide.

di( 3.64]ioxa-7-methyloctyl-l )-xanthogendisulphide,

di( 3.6-dioxadecyll )-xanthogendisulphide,

di( 3oxa-5-isobutoxypentyl-l )-xanthogendisulphide,

. di( 3.6-dioxaundecyl-l )-xanthogendisulphide,

di( 3-oxa-5-istmentoxypentyl-l )-xanthogendisulphide.

di( 3.(w-dioxadmlecyl-l l-xanthogendisulphide,

di( 3-oxa-5isohexoxypentyl-l )-xanthogendisulphide,

di( 3-oxa-hexyl-l )-xanthogendisulphide.

di( 3-oxa-4-methylpentyl-l )-xanthogendisulphide,

di( 3-oxa-heptyl-l )-xanthogendisulphide,

di( Z-isobutoxyethyl-l )-xanthogendisulphide.

di( 3-oxaoctyl-l )-xanthogendisulphide,

di( Z-isopentoxypentyl-l )-xanthogendisulphide,

ROH+MeOH+CS )RO-C-S-Me+I-I di( 3-oxanonyl-l l-xanthogenclisulphide, di( Z-isohexoxyethyl-l )-xanthogendisulphide,

- di( Z-methyl-S-oxabutyl-l )-xanthogendisulphide, di( l-methyl-3-oxabutyl-l )-xanthogendisulphide di( 2-methyl-3-oxapentyl-l )-xanthogendisulphide, di( l-methyl-3-oxapentyl-l )-xanthogendisulphide, di( -oxahex'yl-l )-xanthogendisulphide. di( methoxyisobutyl )-xanthogendisulphide di( 5-oxaheptyl-l l-xanthogendisulphide. di( 3-methyl-4-oxapentyl-l )-xanthogendisulphide. di( l-ethoxymethyl-3-oxapentyl-1 )-xanthogendisulphide.

The invention also relates to a process for producing dialkoxyxanthogendisulphides of formula (I) wherein an alcohol ROH (R as defined above) is reacted with carbon disulphide in the presence of an alkali metal form to from the corresponding alkali xanthogenate which is then oxidised to form the corresponding xanthogcndisulphide. Examples of suitable alcohols ROH are:

l. diethyleneglycol monomethyl ether 2. diethylene glycol monoethyl ether 3. diethylene glycol monopropyl ether 4. diethylene glcyol monoisopropyl ether 5. diethylene glcyol monobutyl ether 6. diethylene glycol monoisobutyl ether 7. diethylene glycol monopentyl ether 8. diethylene glycol monoisopentyl ether 9. diethylene glycol monohexyl ether diethylene glycol monoisohexyl ether ethylene glycol monopropyl ether 12. ethylene glycol monoisopropyl ether ethylene glycol monobutyl ether ethylene glycol monoisobutyl ether ethylene glycol monopentyl ether ethylene glycol monoisopentyl ether ethylene glycol monohexyl ether ethylene glycol monoisohexyl ether propylene glycol monomethyl ether isopropylene glycol monomethyl ether propylene glycol monoethyl ether 22. isopropylene glycol monoethyl ether 3. butylene glycol monomethyl ether isobutylene glycol monomethyl ether butylene glycol monoethyl ether 3-methoxy-l-butanol 27. 1,3-glycerin diethyl ether.

The process is generally carried out as follows: An alcohol ROH (R as defined above) and an aqueous alkali metal hydroxide solution are mixed to about 0 to 30C so that the amounts of alcohol and of hydroxide are equimolar or approximately equimolar. The aqueous alkali metal hydroxide solution is preferably 20 to percent by weight. The preferred alkali hydroxides are sodium and potassium hydroxides.

Carbon disulphide is slowly added to this mixture in an amount from I to l() times the equimolar amount of the alcohol. An exothermic reaction sets in at once and the reaction temperature is kept within the limits of 0 to 50C by external cooling. In this reaction the alkali xanthogenate of the alcohol is formed as illustrated in the following equation:

to w to to out-P Me alkali metal: R as defined above.

To the resulting aqueous alkali xanthogenate solution there is then added a suitable oxidising agent in an amount of from 0.5 to 0.7 mols per mol of alkalixanthogenate, such as hydrogen peroxide or potassium pcroxy disulphate (in the form of an aqueous solution at a temperature of 10 to 40C, preferably 20C, causing formation of the corresponding xanthogendisulphide. This product is water-insoluble and precipitates. It is separated from the aqueous phase (for example by filtration) and dried. The reaction taking place is illustrated in the following equation:

2R-O -S R- R as defined above.

This process is analogous to the known process for producing dialkylxanthogcndisulphides described for example in KirkOthmcr, Encyclopedia of Chemical Technology, 2nd Edition, Vol. 22 1970). pages 419 429, and in Ullmann, Enqvc'lupedic der "ll'clmisclu'n Clu'mic, Vol. 18 (1967) pages 718 728.

The invention also relates to a process for polymerising conjugated diolefins and for copolymerising conjugated diolefins with a-olefins in the presence of radical initiators and of dialkoxyxanthogendisulphides of formula (l) as molecular weight regulators. Suitable conjugated diolefins include those having 4 to 8 carbon atoms, such as butadiene, isoprene and piperylene. Chloroprene and 2,3-dichlorobutadicnc are preferred. Acrylonitrile, styrene and ethyl acrylate are preferred a-olefins. a-olefins can be copolymerised in quantities of up to 40 percent by weight, based on the diolefm. Examples of suitable radical polymerisation catalysts include peroxides, azo compounds and so-called redox systems, i.c., combinations of peroxides and reducing compounds, such as: cumcne hydroperoxide, pinane hydroperoxide, potassium peroxy disulphate, tert.- butyl hydroperoxide, azo-bis-isobutyronitrile; as well as cumcne hydroperoxide, combined with formaldehyde sulphoxylate, iron salts or formamidine sulphinic acid.

Polymerisation is preferably carried out in aqueous emulsion, starting with an aqueous phase containing an emulsifier preferably in a quantity of from 0.1 to percent by weight. Examples of suitable emulsifiers include alkali alkyl sulphonates, alkali alkyl sulphates, long-chain earboxylic acids, resinic acids and polyether alcohols. The monomer or monomers is/are emulsified into the aqueous phase together with from 0.05 to percent by weight, preferably from 0.15 to 1 percent by weight, based on monomer, of a dialkoxyxanthogendisulphide of formula (1). Subsequently the radical initiator is added. Polymerisation temperatures of to +100C and preferably 5 to 50C are suitable (emulsion polymerisation of chloroprene is basically known see e.g., U.S. Pat. Nos. 3,042,652, 3,147,317 and 3,147,318).

At a conversion of 50 to 100 percent, preferably 50 to percent, polymerisation is terminated. any unreactcd monomer is removed, the polymer formed precipitated from the aqueous emulsion with an electrolyte or by low-temperature coagulation and then dried in the usual way. The dialkoxyxanthogendisulphides function as molecular weight regulators; they reduce the molecular weight of the polymers obtained compared with polymers made in their absence. This is demonstrated by comparing Mooney viscosities.

The dialkoxyxanthogendisulphides of the invention are especially molecular weight regulators in the polymerisation of chloroprene. Polychloroprene obtained in their presence has particularly favourable processing properties. These are most pronounced in mixtures of uncrosslinked benzene-soluble polychloroprenes produced in accordance with the invention and crosslinked benzene-insoluble polychloroprenes. In addition to favourable processing properties, these mixtures also have particularly high strength.

Accordingly, the invention also relates to a mixture of an uncrosslinked benzene-soluble chloroprene polymer (a) and a crosslinked benzene-insoluble chloroprene polymer (b), wherein the uncrosslinked benzene-soluble chloroprene polymer is a polymer ofchloroprene and optionally up to 40 percent by weight (based on monomer mixture) of an a-olefin prepared in the presence of from 0.05 to 30 percent by weight (based on monomer) of a dialkoxyxanthogendisulphide of formula (1).

Accordingly. the benzene-soluble chloroprene polymer in this mixture is a product the preparation of which has been described above.

Crosslinked benzene-insoluble chloroprene polymers suitable for admixture with benzene-soluble chloroprene polymers can be obtained in latex form by various methods. For example, conventional chloroprene polymerisation can be continued to high (e.g., to percent) conversion with no or only a small quantity of a chain-transfer agent, such as an alkyl mercaptan or a dialkylxanthogendisulphide. Such a process is described for example in U.S. Pat. No. 3,147,317. Alternatively chloroprene is eopolymerised with a copolymerisable monomer containing two or more polymerisable double bonds. Examples of suitable comonomers include divinyl benzene and esters of methacrylic acid with polyhydroxy compounds, for example alkylene glycols. dihydroxy benzene or trimethylol propane, containing at least two methacrylic acid moieties.

in general, crosslinked chloroprene polymers are made by the same basic process which yields benzenesolublc chloroprene polymers, the only difference being that monomer conversion is increased, for example to from 90 to 100 percent.

In another method of producing suitable crosslinked chloroprene polymers a latex of a benzene-soluble chloroprene polymer is subjected to a crosslinking post-treatment. Examples of suitable post-treatments are irradiation with actinic light as described in U.S. Pat. No. 3,042,652 and treatment with an organic peroxy compound as described in U.S. Pat. No. 3,147,318.

1n the crosslinked chloroprene polymers up to about 20 percent of the chloroprene can be replaced by another conjugated diolefins or a-olefins, examples of which are given in the description relating to the preparation of the benzene-soluble chloroprene polymers.

A copolymer of chloroprene and from 2 to 20 percent by weight, based on chloroprene. of a diester of a dihydric aliphatic alcohol and an acrylic acid, is a preferred benzene-insoluble chloroprene polymer. These diesters correspond to the general formula (11):

HC CH I n a I R10 OR isobutylene diaerylate.

Such copolymers are made by the conventional aqueous emulsion polymerisation used for making polychloroprene. These eopolymers and the process for their manufacture are described in British Pat. No.

Mixtures of crosslinked and non-crosslinked chloroprene polymers are made. e.g. by thoroughly mixing them in latex form and subsequently recovering the solid polymer mixture. for example by low-temperature Coagulation (as described in US. Pat. No. 2.187.146) or by drying on cylinders (as described in US. Pat. No. 2,914.49? It is also possible to mix the solid polymers mechanically. for example by kneading on mixing rolls or in an internal mixer (such as a Banbury mixer or a Werner-Pfleidercr mixer).

The weight ratio of the benzene-soluble dialkoxyxanthogendisulphide modified chloroprene polymer (a) to the crosslinked chloroprene polymer (b) is preferably from about 2():l to I11 most preferably from 4:] to lzl.

The polychloroprene mixtures of the invention can be processed to form rubber mixtures and vulcanised in the same way as conventional polychloroprenes. They can be used for all purposes ofconventional polychloroprenes. Their particular advantage is improved processing compared to benzene-soluble and benzeneinsoluble polychloroprenes and improved stability under thermal stress compared with mixtures of conventional benzene-soluble and benzene-insoluble polychloroprenes.

Preparation of alkoxyxanthogendisulphides:

EXAMPLE I The xanthogendisulphide of diethylene glycol monoethyl ether 88 g of sodium hydroxide are dissolved in 90 g of pure water in a 3-litre-flask with stirring. 268 g ofdiethylene glycol monoethyl ether are then added and the A solution of 300 g of ammonium persulphate in 2 litres of pure water is then run into the obtained reaction mixture of the xanthogenate formed. The xanthogendisulphide formed by oxidation precipitates, is filtered off. washed with pure water, and redissolved in ether. The ether solution is dried with anhydrous sodium sulphate and the ether evaporated on a rotary evaporator. The yield of xanthogendisulphide is 22] g.

The xanthogendisulphidc of B-methoxy-l-butanol 88 g of sodium hydroxide are dissolved in 90 g of pure water in a 3-litre flask with stirring. 208 g of 3 25 methoxy-l-butanol are then added. and the mixture stirred for a further 2 hours. After cooling to C 176 g ofcarbon disulphide are added dropwise with stirring so that the temperature does not exceed C; stirring is continued for a further 2 hours. a solution of 300 g of ammonium persulphate in 2 litres of pure water is then run into the obtained reaction mixture ofthe xanthogenate formed. The xanthogendisulphide formed by oxidation precipitates, is filtered off. washed with pure water and redissolved. The ether solution is dried with anhydrous sodium sulphate and theether evaporated on a rotary evaporator. The yield of xanthogendisulphide is 310 g.

mixture stirred for 2 hours. After cooling to IOC 176 H g ofcarbon disulphide are added dropwise with stirring, 3 1 2 2 u u 2 2 r 3 so that the temperature does not exceed 20C; stirring OCH S S OCH is continued for a further 2 hours.

A solution of 300 g of ammonium persulphate in 2 litres of pure water is then run into the obtained reac- EXAMPI E 4 tion mixture of the xanthogenate formed. The xanthogcndisulphide formed by oxidation precipitates, is filtered off. washed with pure water and redissolved in ethylether. The ether solution is dried with anhydrous evaporator. The yield of xanthogendisulphide is 297 g.

EXAMPLE 2 The xanthogemlisulphide of l.3-glycerin diethyl ether l5() g of sodium hydroxide are dissolved in ISO g of pure water in a 3-litre flask with stirring. 2% g of glycerin-l .3-diethyl ether are then added and the mix- The xanthogendisulphide of propoxy ethylene glycol 88 g of sodium hydroxide are dissolved in 90 g of a pure water in a 3-litre flask with stirring. 208 g of sodium sulphate and the ether evaporated on a rotary 0 propoxy ethylene glycol are then added and stirring continued for 2 hours.

-CH OC H After cooling to l()C I76 g of carbon disulphide are added dropwise with stirring so that the temperature turc stirred for 2 hours. After cooling to 10C I52 g of thogendisulphide formed by oxidation precipitates, is

carbon disulphide are added dropwise with stirring, so that the temperature does not exceed 20C; stirring is continued for a further 2 hours.

filtered off. washed with pure water and redissolved in ether. The ether solution is dried with anhydrous sodium sulphate and the ether evaporated in a rotary evaporator. The yield is 3 3 g.

tion product of naphthalene sulphonic acid and Alkoxyxanthogendisulphides as molecular weight regulators:

I. Polymerisation example The following phases are separately prepared and introduced into the reaction vessel: Monomer phase 100 parts by weight of chloroprene and y parts by weight of the xanthogendisulphide of 3- methoxy- I -butanol Aqueous phase 120 parts by weight of pure water,

parts by weight of the sodium salt of a disproportionatcd abietic acid,

0.5 parts by weight of the sodium salt of a condensation product of naphthalene sulphonic acid and formaldehyde,

0.5 parts by weight of sodium hydroxide, and

0.5 parts by weight of tetrasodium pyrophosphate.

y was selected as follows:

The value for the quantity of regulator y was varied as follows:

y, 0.3 parts by weight,

y. 0.6 parts by weight,

0.65 parts by weight,

y 0.70 parts by weight,

y 0.75 parts by weight, and

y 0.80 parts by weight.

After the two phases have been mixed, the temperature is increased to 43C and polymerisation initiated by an activator solution of 2.5 parts by weight of formamidine sulphinic acid in 97.5 parts by weight of pure water. The activator solution is added dropwise.

At the monomer conversion of 65 to 70 percent, the residual monomer is removed by steam distillation and the polymer recovered from the latex formed by precipitation with an electrolyte and dried. Table I shows Mooney viscosities ML-4/I00C of the polymers.

Table I y regulator Mooney viscosity '7 by weight (ML-4' at I00(') y 0.3 I22 y 0.6 65 y 0.65 52 0.70 42 y 0.75 34 (um 30 formaldehyde,

0.5 parts by weight of sodium hydroxide, and

0.5 parts by weight of tetrasodium pyrophosphate.

: was selected as follows:

.1. 0.6 part by weight, and

: 1.0 part by weight.

After the two phases have been mixed. the temperature is increased to 43C and polymerisation initiated by an activator solution of 2.5 parts by weight of formamidine sulphinic acid and 97.5 parts by weight of pure water. The activator solution is added dropwise.

At a monomer conversion of 65 to percent, the residual monomer is removed by steam distillation, the polymer recovered from the latex formed by precipitation with an electrolyte and dried. Table 2 indicates Mooney viscosities of the products made. I

Ill. Polymerisation example The following phases are separately prepared and introduced into the reaction vessel: Monomer phase I parts by weight of chloroprenc, and

1' parts by weight of the xanthogendisulphide ofdiethylene glycol monoethyl ether.

Aqueous phase parts by weight of pure water,

5 parts by weight of the sodium salt of a disproportionatcd abietic acid,

0.5 part by weight of the sodium salt of a condensation product of naphthalene sulphonic acid and formaldehyde,

0.5 part by weight of sodium hydroxide, and

0.5 part by weight of tetrasodium pyrophosphate.

r was selected as followsf r 0.3 part by weight, and

r 0.6 part by weight.

After the two phases have been mixed. the temperature is increased to 43C and polymerisation initiated by an activator solution of 2.5 parts by weight of formamidine sulphinic acid and 97.5 parts by weight ofpure water. The activator solution is added dropwise.

At a monomer conversion of 65 to 70 percent, the residual monomer is removed by steam distillation and the polymer recovered from the latex formed by precipitation with an electrolyte and dried. Table 3 indicates Mooney viscosities of the products obtained.

IV. Polymerisation example Aqueous phase 72 parts by weight of pure water. 3 parts by weight of the sodium salt of an alkyl sulphate 0.4 part by weight of the sodium salt ofthe condensation product of naphthalene sulphonic acid and formaldehyde,

l part by weight of tetrasodium pyrosulphatc, and

0025 parts by weight of sodium hydroxide. Monomer phase 27 parts by weight of acrylonitrile, and

0.66 part by weight of the xanthogendisulphide of 3- methoxyl -butanol.

The phases are separately prepared and introduced into a reaction vessel. 63 parts by weight of butadiene are then introduced under pressure.

After mixing. the temperature is adjusted to 20C and polymerisation activated with l percent by weight, based on monomers, of potassium persulphate. At a monomer conversion of approximately 75 percent. the residual monomer is removed, the latex stabilised and the polymer precipitated from the latex with an electrolyte and subsequently dried.

The polymer has a Mooney viscosity ML-4/l00C of about 45. If no xanthogendisulphide is present in this polymerisation. Mooney viseosities ML-4'/l00C above 200 are found.

V. Polymerisation example Preparation of a mixture of a benzene-soluble chloroprene polymer and a benzene-insoluble chloroprene polymer.

l. Preparation of the benzene-insoluble chloroprene polymer Into a 40-litre autoclave equipped with stirrer, thermometer, inlet pipes and a cooling system are introdueed:

l4.4 litres of desalted water, 8l5 g of the sodium salt of a disproportiomtted abietic acid mixture, 72 g of a condensation product of alkyl naphthalene sulphonic acid and formaldehyde. 36 g of sodium hydroxide and 60 g of tetrasodium pyrophosphatc. Then a mixture of 10 620 g of chloroprene, L380 g of ethylene glycol dimethacrylate and 34 g of n-dodecyl mercaptan is added. The resulting mixture is then heated to 43C and polymerisation is initiated by adding a catalyst solution of 5 got formamidine sulphinic acid in 150 g of pure water.

At a conversion of approximately 80 percent, polymerisation is stopped by adding a stabiliser solution of:

5 g of phenothiazine and 5 g of p-tert.-butyl pyrocatechol in 500 g of benzene. The resulting polymer latex is then freed from unreacted monomer. 2. Preparation of the benzene-soluble chloroprene polymer A polymer latex is made in accordance with polymerisation example I using 0.60 parts by weight of the xanthogendisulphide of 3-methoxy-l-butanol. 3. Preparation of a benzene-soluble chloroprene polymer for comparison in the absence of alkoxyxantlmgendisulphide is carried out in accordance with polymerisation example I using 0.59 parts by weight of diisopropylxanthogendisulphide.

Admixture of benzene-soluble and benzene-insoluble polychloroprene:

Mixture A i The polychloroprene latex of Example V 2 is mixed with the polychloroprene latex according to Example V I so that the mixture contains 85 parts by weight of the benzene-soluble polyehloroprene and parts by weight of the benzene-insoluble polyehloroprene. The solid polychloroprenc mixture is recovered from the latex mixture by low-temperature coagulation, separation and drying of the solids. Mixture B Mixture B (for comparison) is prepared from the latices of examples V 3 and V l in exactly the same way as described in A.

Samples of products A and B are stored at 70C and the change in their Mooney viscosities over the storage period determined. The results are set out in the following Table:

, Product Mooney viscosity ML-4 [00C) Increase in t after storage for y-days Mooney viscosity after 3 days y=0 y=l \=2 \'=3 B 52 55 60 ()7 l5 A 51 53 54 54 3 Product A (according to the invention) shows practically no change in viscosity and is thus considerably more stable under heat than product B (comparison).

What is claimed is:

l. A dialkoxyxanthogendisulphide of the formula R-O-C-S-SC-0R II II wherein the R's are equal or different and each repre sents R10 CH2 a l m wherein R is alkyl having I to 10 carbon atoms;

R: is linear or branched alkylene having 3 to 10 carbon atoms: R;, is alkyl having 3 to l0 carbon atoms; :1 and n are 2. 3 or 4: and m is l or 2. 2. The dialkoxyxanthogendisulphide of claim I wherein R is -CH CH- ,OCH. ,CH OC H 3. The dialkoxyxanthogendisulphide of cliam 1 wherein R is 3,875,201 11 ,12 4. The dialkoxyxanthogcndisu]phide of clzii n i l 5. The dialkoxyxanthogcndiSu Iphidc of claim 1 wherein Ris v v wherein R is 

1. A DIALKOCYXANTHOGENDISULPHIDE OF THE FORMULA
 2. The dialkoxyxanthogendisulphide of claim 1 wherein R is -CH2-CH2-O-CH2-CH2-OC2H5.
 3. The dialkoxyxanthogendisulphide of cliam 1 wherein R is
 4. The dialkoxyxanthogendisulphide of claim 1 wherein R is
 5. The dialkoxyxanthogendisulphide of claim 1 wherein R is -CH2-CH2-O-CH2-CH2-CH3. 